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package org.apache.juneau.rest;

import java.io.*;
import java.lang.reflect.*;
import java.util.*;

import javax.servlet.*;
import javax.servlet.http.*;

import org.apache.juneau.*;
import org.apache.juneau.config.*;
import org.apache.juneau.dto.swagger.*;
import org.apache.juneau.http.*;
import org.apache.juneau.http.Date;
import org.apache.juneau.parser.*;
import org.apache.juneau.utils.*;

/**
 * REST java method parameter resolver.
 * 
 * <p>
 * Used to resolve instances of classes being passed to Java REST methods.
 * 
 * <p>
 * By default, the following parameter types can be passed into Java methods in any order:
 * 
 * <h5 class='topic'>Standard top-level objects</h5>
 * <ul>
 * 	<li><b>Standard top-level objects</b>
 * 	<ul>
 * 		<li class='jc'>{@link HttpServletRequest}
 * 		<li class='jc'>{@link RestRequest}
 * 		<li class='jc'>{@link HttpServletResponse}
 * 		<li class='jc'>{@link RestResponse}
 * 	</ul>
 * 	<li><b>Headers</b>
 * 	<ul>
 * 		<li class='jc'>{@link Accept}
 * 		<li class='jc'>{@link AcceptCharset}
 * 		<li class='jc'>{@link AcceptEncoding}
 * 		<li class='jc'>{@link AcceptLanguage}
 * 		<li class='jc'>{@link Authorization}
 * 		<li class='jc'>{@link CacheControl}
 * 		<li class='jc'>{@link Connection}
 * 		<li class='jc'>{@link ContentLength}
 * 		<li class='jc'>{@link ContentType}
 * 		<li class='jc'>{@link Date}
 * 		<li class='jc'>{@link Expect}
 * 		<li class='jc'>{@link From}
 * 		<li class='jc'>{@link Host}
 * 		<li class='jc'>{@link IfMatch}
 * 		<li class='jc'>{@link IfModifiedSince}
 * 		<li class='jc'>{@link IfNoneMatch}
 * 		<li class='jc'>{@link IfRange}
 * 		<li class='jc'>{@link IfUnmodifiedSince}
 * 		<li class='jc'>{@link MaxForwards}
 * 		<li class='jc'>{@link Pragma}
 * 		<li class='jc'>{@link ProxyAuthorization}
 * 		<li class='jc'>{@link Range}
 * 		<li class='jc'>{@link Referer}
 * 		<li class='jc'>{@link TE}
 * 		<li class='jc'>{@link TimeZone}
 * 		<li class='jc'>{@link UserAgent}
 * 		<li class='jc'>{@link Upgrade}
 * 		<li class='jc'>{@link Via}
 * 		<li class='jc'>{@link Warning}
 * 	</ul>
 * 	<li><b>Other objects</b>
 * 	<ul>
 * 		<li class='jc'>{@link Config}
 * 		<li class='jc'>{@link HttpMethod}
 * 		<li class='jc'>{@link InputStream}
 * 		<li class='jc'>{@link Locale}
 * 		<li class='jc'>{@link MessageBundle}
 * 		<li class='jc'>{@link OutputStream}
 * 		<li class='jc'>{@link Parser}
 * 		<li class='jc'>{@link Reader}
 * 		<li class='jc'>{@link RequestBody}
 * 		<li class='jc'>{@link RequestFormData}
 * 		<li class='jc'>{@link RequestHeaders}
 * 		<li class='jc'>{@link RequestPathMatch}
 * 		<li class='jc'>{@link RequestQuery}
 * 		<li class='jc'>{@link ResourceBundle}
 * 		<li class='jc'>{@link RestContext}
 * 		<li class='jc'>{@link RestLogger}
 * 		<li class='jc'>{@link RequestProperties}
 * 		<li class='jc'>{@link ServletInputStream}
 * 		<li class='jc'>{@link ServletOutputStream}
 * 		<li class='jc'>{@link Swagger}
 * 		<li class='jc'>{@link UriContext}
 * 		<li class='jc'>{@link UriResolver}
 * 		<li class='jc'>{@link Writer}
 *  	</ul>
 * </ul>
 * 
 * <h5 class='section'>See Also:</h5>
 * <ul>
 * 	<li class='jf'>{@link RestContext#REST_paramResolvers}
 * 	<li class='link'><a class="doclink" href="../../../../overview-summary.html#juneau-rest-server.MethodParameters">Overview &gt; juneau-rest-server &gt; Java Method Parameters</a>
 * </ul>
 */
public abstract class RestParam {

	final RestParamType paramType;
	final String name;
	final Type type;

	/**
	 * Constructor.
	 * 
	 * @param paramType The Swagger parameter type.
	 * @param name
	 * 	The parameter name.
	 * 	Can be <jk>null</jk> if parameter doesn't have a name (e.g. the request body).
	 * @param type The object type to convert the parameter to.
	 */
	protected RestParam(RestParamType paramType, String name, Type type) {
		this.paramType = paramType;
		this.name = name;
		this.type = type;
	}

	/**
	 * Resolves the parameter object.
	 * 
	 * @param req The rest request.
	 * @param res The rest response.
	 * @return The resolved object.
	 * @throws Exception
	 */
	public abstract Object resolve(RestRequest req, RestResponse res) throws Exception;

	/**
	 * Returns the parameter class type that this parameter resolver is meant for.
	 * 
	 * @return The parameter class type, or <jk>null</jk> if the type passed in isn't an instance of {@link Class}.
	 */
	protected Class<?> forClass() {
		if (type instanceof Class)
			return (Class<?>)type;
		return null;
	}

	/**
	 * Returns the swagger parameter type for this parameter as shown in the Swagger doc.
	 * 
	 * @return the swagger parameter type for this parameter.
	 */
	protected RestParamType getParamType() {
		return paramType;
	}

	/**
	 * Returns the parameter name for this parameter as shown in the Swagger doc.
	 * 
	 * @return the parameter name for this parameter.
	 */
	protected String getName() {
		return name;
	}

	/**
	 * Returns the parameter class type.
	 * 
	 * @return the parameter class type.
	 */
	public Type getType() {
		return type;
	}
}
